Process for the recovery of iodine from aqueous solutions containing iodinated organic compounds

ABSTRACT

A process for the recovery of iodine from mother liquors or wastes containing iodinated organic compounds, by mineralisation of organic iodine and subsequent transformation of the formed iodide into elementary iodine, characterized in that the aqueous solution is concentrated to a suitable volume before the mineralisation step, under atmospheric pressure and at the boiling temperature, and said solution is purified by nanofiltration.

DISCLOSURE

The present invention relates to a novel process for the recovery ofiodine from solutions containing iodinated organic compounds, inparticular non-ionic contrast agents.

The most modern contrast agents, i.e. the non-ionic ones, are usually2,4,6-triiodo-1,3-benzenedicarboxylic acid derivatives, characterized bya strong bond of the iodine atoms to the aromatic ring. The strength ofsaid bond is however also affected by the structure of the concernedcompound.

Due to environmental reasons, the effluents should be completely freefrom iodinated organic compounds, while for economic reasons as muchiodine as possible should be recovered, in that it is now rare andexpensive. In this case, economic and environmental needs meet.

The problem has arisen for some time, as evidenced by a series ofpatents concerning this process (see for example: WO 98/07661; WO94/10083; NO 9100001; EP 106934). In particular, EP 106934, filed in theApplicant' name in 1982, discloses the process for the mineralisation ofiodine, which comprises heating the solutions of the contrast agents for30 minutes-2 hours at 100-150° C. in a strong alkali excess in thepresence of 100 to 2500 ppm of copper ions or of finely dispersedcopper.

The recovery of iodine after mineralisation is carried out according toknown methods, usually by oxidation of the formed iodide with mildmeans. The formed iodine is recovered and concentrated, for example, byextraction or by sublimation in air or vapour stream. Iodine can also berecovered from the extraction solvent (for example toluene) by treatmentwith aqueous alkali hydroxide, and the iodine vapours obtained in thesublimation can be collected, for example, through absorption in alkalihydroxide solutions by iodide-iodate dismutation.

Iodine is known to quantitatively regenerate from the alkali hydroxidesolution by acidification following dismutation.

It can easily be evinced from EP 106934 (page 6, Table) that thetemperature of the mineralisation process depends on the type of thecontrast agent.

The conditions for the preparation of Iopamidol and Metrizamide, whichthen represented the novel class of non-ionic compounds (i.e. in whichthe carboxylic groups are in the form of amides with aminoalcohols), aremore drastic than those for the ionic compounds, i.e. those having atleast one acid group on the aromatic ring (acetrizoic, diatrizoic,iothalamic, iopronic, iopanoic acids, iodamide and adipiodone). Forexample, the best results are achieved when heating the 2% Iopamidolsolution to 150° C. in the presence of 2500 ppm of copper ion.

The most diffused compounds are at present the non-ionic ones. Thepreparation thereof usually involves crystallizations from a solvent,usually alcoholic, both in the intermediate steps and the final one.

The presence of solvents in wastes from which iodine has to be recoveredmakes carring out the cited process more difficult, particularly in thefollowing steps:

when the mineralisation process is carried out, according to theteaching of the Patent, at least at 100° C., it is difficult to reachsaid temperature due to the low-boiling organic solvent (such as a loweralcohol), unless operating under pressure;

the presence of the solvents, in particular alcohols, makes theprecipitation of iodine after sublimation problematic, unless using asystem of scrubber;

when using an alternative process for recovering the sublimated iodine(treatment with alkali and subsequent precipitation of iodine byacidification), side-formation of iodoform takes places due to thepresence of compounds having RCOCH₃/RCHOHCH₃ groups.

Said reaction, which has to be absolutely avoided for environmentalreasons, also prevents the recovery of iodine due to the precipitationof iodoform.

finally, it is necessary to increase the amount of oxidizer necessary tooxidize the iodide formed after mineralisation.

A further technical problem which had not been evidenced in the abovePatent is that, after the mineralisation step, phenol or quinone organiccompounds are present which cause a consumption of oxidizer in thesubsequent oxidation step and moreover have a high environmental impact,in that they are not biodegradable.

It has now surprisingly been found that the above cited problems can besolved by concentrating the solution obtained under the mineralisationconditions described in EP 106,934 and purifying said solution bynanofiltration before the oxidative step, thereby improving the overallyield of process.

It is therefore an object of the present invention a process for therecovery of iodine from mother liquors or wastes with a percentage oforganic solvents at most of 95% (w/w), containing iodinated organiccompounds, by mineralisation of organic iodine (in the presence ofcopper ions or finely dispersed metallic copper in alkali aqueoussolution) and subsequent transformation of the formed iodide intoelementary iodine, characterized in that the aqueous solution, aftermineralisation, is concentrated under atmospheric pressure and at theboiling temperature and is subsequently subjected to nanofiltration.

The process is particularly suitable for the treatment of solutions ofnon-ionic iodinated contrast agents, such as: Iopamidol, Iohexol,Iopromide, Ioxilan, Iomeprol, Iopentol, Ioversol. The process of theinvention can also be applied to ionic contrast agents, if the abovestated conditions are fulfilled. In this case, aqueous or organicsolvents solutions will be present, depending on compound or waste to betreated and on the synthetic step.

The solution is preferably adjusted to a volume ranging from 85% to 25%(w/w) of the starting volume. Said procedure is easily applicable towaste solutions from the synthesis of ionic or non-ionic contrastagents, possibly in the presence of solvents, and it allows to decreasethe COD from values of 20.000-40.000 mg/L to 4.000-9.000 mg/L throughdemolition of the organic molecules present and removal of any solvents.

The conditions of the mineralisation process of the present inventionare the same as those disclosed in EP 106,934.

The copper catalyst is added in amounts from 100 to 3000 ppm, preferably500-1000 ppm, and pH is kept at 12 during the whole mineralisation step.

The process of the invention comprises heating the solution to bedeiodinated at the boiling temperature and under atmospheric pressure.

This, of course, involves rather long times such as:

4 to 6 hours for mineralising a solution of Iopamidol, Iomeprol,Iohexol, Metrizamide or of a generic non-ionic contrast agent, inconcentration of 2%-10% (w/w) with an at most 95% (w/w) content inalcoholic solvent;

2 to 3 hours for mineralising a solution of the mother liquors from theproduction of Iopamidol intermediates containing 3%-15% (w/w) ofiodinated intermediate, with the following maximum contents (w/w):2-butanol 20%, methylchloroform 5%, n-butyl acetate 4%, n-dodecane 3%(w/w) and tert-butanol 30%. As mentioned above, the process of theinvention can also be used for mother liquors from production cycles ofother ionic contrast agents such as:

3,5-acetylamino-2,4,6-triiodo-benzoic acid sodium salt (DIAC),acetrizoic acid (3-acetamino-2,4,6-triiodobenzoic acid);

adipione(3,3′-[(I,1,6-dioxo-1,6-hexanediyl)diimino]-bis-2,4,6-triiodobenzoicacid;

iodossamic acid(3,3′-[(1,16-dioxo-4,7,10,13-tetraoxahexadecane-1,16-diyl)diimino]-bis-2,4,6-triiodobenzoic acid;

iothalamic acid(3-(acetylamino)-2,4,6-triiodo-5-[(methylamino)carbonyl]-benzoic acid;

iopronic acid (2-[[2-[3-(acetylamino-2,4,6-triiodo-phenoxy]ethoxy]methyl]butanoic acid;

iopanoic acid, 3-amino-α-ethyl-2,4,6-triiodobenzenepropionic acid.

The above Patent did not envisage any concentration or elimination stepof the organic solvents (see examples 1, 2, 4, 5, 7, 27, 55).

In Examples 3 and 6, concerning non-ionic contrast agents (Iopamidol andMetrizamide) it is even necessary to use an autoclave or a sealedcontainer to carry out the mineralisation at 130-150° C. for 1 hour.

Conversely, a feature of the process of the invention is a concentrationstep under atmospheric pressure, which avoids the use of an autoclave,making use of the ebullioscopic raising due to the solids present at105-120° C. and increasing the duration of the step by 2-6 hours. Whenthe solutions do not contain salts dissolved so as to guarantee theebullioscopic raising, sodium sulfate and/or sodium chloride can beadded to produce such an effect. The amounts to be added depend on themixture to be mineralised.

Operating this way, any solvents present are removed by either direct orvapour stream distillation while carrying out the mineralisation ofiodine.

This is particularly important in the case of lower alcohols which arethe most used solvents in the processes for the preparation of non-ioniccontrast agents which comprise a final crystallization and which cangive rise to iodoform, as already mentioned.

Furthermore, the solution to be fed to the subsequent step isconcentrated, which is particularly useful in case it allows to removesome inorganic salts less soluble than sodium iodide.

This simple operation provides a significant decrease in thecontamination load with an increase in biodegradability. For example, ina production waste of Iopamidol, starting from a COD of 25.000 mg/L anda BOD of 1.500 mg/L, a solution can be obtained with COD 7.000 and BOD3.500 at the end of the mineralisation. This reduction is due theelimination of the solvents and to the partial degradation of thearomatic molecules.

It is also possible to include a filtration step of the solution aftermineralisation and a concentration step when high concentrations ofpoorly soluble saline compounds are present, which can precipitate inthe concentration step (in particular the precipitation of Na₂SO₄·10 H₂Ocan take place).

Filtration provides the advantage of removing part of the ioniccompounds present in solution, thereby reducing the osmotic pressure inthe subsequent nanofiltration step.

The solution, after mineralisation, concentration and optionalfiltration, is purified by nanofiltration. Said operation is carried outin two steps:

1. nanofiltration of the solution;

2. diafiltration with addition of water so as to adjust the permeatedsolution to about the starting volume before the mineralisation step.

The process of the present invention surprisingly employs this techniquekeeping the permeate instead of the retentate, which is more commonlythe purified fraction. In this case, the solution from which the iodineis recovered is the permeate, mainly containing sodium iodide, purifiedfrom the high molecular organic substances and from sodium sulfate andany sodium sulfite.

The iodide concentration of the permeate ranges from 0.6 to 1.4%,evaluated by argentometric titration.

The final step for the recovery of solid iodine is effectedconventionally, as cited above.

Particularly preferred is the use of hydrogen peroxide as oxidizer, atpH 0.5-1.5 by addition of 50% w/w sulfuric acid, at room or hightemperature (20-50° C.), mainly in that the reduced product is water.

The almost complete absence of organic molecules advantageously reducesthe amount of oxidizer necessary. In fact, in the process of theinvention, only a slight excess (5-15%) to the stoichiometric isenvisaged.

The oxidation is substantially instantaneous, as no oxidizableside-products are present, and is monitored by measuring the ox-redoxpotential with a platinum electrode.

The reaction is considered completed at a 480-540 mV of calomel-relativepotential.

The last step is the recovery of iodine by two ways:

1. Filtration of the precipitated iodine, which is possible, contrary tothe prior art, in that only NaCl is present in the solution. To improveprecipitation yields the solution may be concentrated to 30-50% of thestarting volume before the oxidation, guarantying an about 3% iodinecontent. Total yields are about 88-90% on theoretical.

2. Sublimation of precipitated iodine in vapour stream, absorption inalkali (preferably 30% NaOH) as I⁻/IO₃ ⁻ at a iodine maximumconcentration of 3.5% and precipitation by acidification. In this case,total yields are about 90-95% on theoretical.

According to a further aspect of the invention the oxidation andrecovery of iodine are carried out in a single step.

The permeate from the nanofiltration step is acidified to pH 0.5-1 with50% sulfuric acid, at temperatures ranging from 20° C. to 50° C. Saidsolution is fed to a continuous extractor adding the oxidizer in line soas to guarantee a permanence time sufficient for the complete oxidationand extraction. Iodine is extracted with a suitable solvent (such astoluene, methyl tert-butyl ether, dodecane). This way iodide is oxidizedto iodine and extracted from the aqueous solution in a single industrialoperation. Iodine is extracted from the solvent by treatment with basesand then recovered as already described above. The overall yield is, inthis case, about 93-96% on theoretical.

The following examples illustrate the best experimental conditions tocarry out the process of the invention.

EXPERIMENTAL SECTION EXAMPLE 1

30 kg of mixture of effluents from the production of Iopamidol,containing about 4% (w/w) of organic solvents (2-butanol, butyl acetate,diglyme, tert-butanol, dodecane), about 0.4% (w/w) of2,4,6-triiodo-5-amino-1,3-benzenedicarboxylic acid, about 0.9% ofIopamidol and its side-products (the iodine content of the mixture being0.75% (w/w)) are adjusted to pH 12 with 30% NaOH (w/w). 5 9 of CuSO₄·5H₂O are added and the mixture is concentrated under atmospheric pressureto about 80% of the starting weight; then the reaction mixture isrefluxed to complete the mineralisation, so that the total distillationand reflux time is 6 hours.

The mineralisation yield is 100% (determined on the iodine content byargentometric titration compared with the starting content in organiciodine).

The concentrated solution is left to cool and buffered to pH 7 with 50%H₂SO₄ (w/w) then subjected to nanofiltration, using a Separem membranemod. Desals (DK2521T) at an operative pressure of 25-30 bar. Thesolution is diafiltered adding water, keeping the retentate volumesubstantially constant (about 30 L of H₂O are added). The collectedpermeate (30 L) is concentrated to 12 L under atmospheric pressure, thenacidified to pH 1 with 50% H₂SO₄ (w/w) and treated with 30% H₂O₂ (w/w)at room temperature monitoring the redox potential of the solution; thereaction is completed when a 520 mV potential is reached. Theprecipitated elementary iodine is recovered by filtration through porousseptum!.

198 g of elementary iodine are obtained (88% overall yield of theprocess).

EXAMPLE 2

40 kg of mixture of effluents from the production of Iopamidol,containing about 4% of organic solvents (2-butanol, butyl acetate,diglyme, tert-butanol, dodecane), about 0.4% (w/w) of2,4,6-triiodo-5-amino-1,3-benzenedicarboxylic acid and about 0.9% (w/w)of Iopamidol and its side-products (the iodine content of the mixturebeing 0.70% (w/w)) are adjusted to pH 12 with 30% NaOH (w/w). 6 g ofCuSO₄·5 H₂O are added, the mixture is concentrated under atmosphericpressure to 30% of the starting weight, then refluxed to completemineralisation, so that the overall distillation and reflux time is 8hours.

The yield mineralisation is 100% (determined on the iodine content byargentometric titration compared with the starting content in organiciodine).

The concentrated solution is left cool at 15° C. for 2 hours and theprecipitated salts are filtered through porous septum. The solution isbuffered to pH 7 with 50% H₂SO₄ (w/w) and subjected to nanofiltration,using a Separem membrane mod. Desal5 (DK2521T) at an operative pressureof 25-30 bars. The solution is diafiltered, keeping the retentate volumeconstant (about 28 L of H₂O are added).

The recovery of iodine in the permeate is 99% compared with that presentin the solution before nanofiltration.

The collected permeate (30 L) is acidified to pH 1 with 50% H₂SO₄ (w/w).The resulting solution is oxidized at room temperature (25° C.) in acontinuous oxidation-extraction system. Oxidation is carried out feedingin line 30% H₂O₂ (w/w) to the permeate at pH 1: the aqueous solution isthen fed to a continuous laboratory extractor and the elementary iodineformed following oxidation is extracted with dodecane. The amount of 30%H₂O₂ (w/w) used is defined monitoring the redox potential directly atthe head of the extractor keeping it at 530 mV. The used volumetricratios are 3 L of dodecane to 1 L of aqueous solution. 90 L of organicphase are collected.

The extraction yield of iodine, is 98% compared with the amount ofiodine present in the permeation solution from nanofiltration.

The organic phase is again subjected to extraction in a continuoussystem with an aqueous alkali solution (30% NaOH (w/w) in volumetricratio of 1 L to 16 L of organic phase). The resulting alkaline solution(5.6 L) is adjusted to pH 1 with 50% H₂SO₄ (w/w). The precipitatedelementary iodine is recovered by filtration.

257 g of iodine are obtained (overall yield 92% of the process).

EXAMPLE 3

40 kg of mixture of effluents from the production of Iopamidol,containing about 30% (w/w) of organic solvents (2-butanol andtert-butanol), about 10% (w/w) of2,4,6-triiodo-5-amino-1,3-benzenedicarboxylic acid and about 4% (w/w) ofIopamidol and its side-products (the iodine content of the mixture being8.76% (w/w)) are adjusted to pH 12 with 30% NaOH (w/w) 75 g of CuSO₄·5H₂O are added, the mixture is concentrated under atmospheric pressure to30% (w/w) of the starting weight, then refluxed to complete themineralisation, so that the total distillation and reflux time is 8hours.

The mineralisation yield is 100% (determined on the iodine content byargentometric titration compared with the starting content in organiciodine).

The concentrated solution is left to cool at 15° C. for 2 hours and theprecipitated salts are filtered through porous septum. The solution isbuffered to pH 7 with 50% H₂SO₄ (w/w) and subjected to nanofiltration,using a Separem membrane mod. Desal5 (DK2521T) at an operative pressureof 25-30 bars. The solution is diafiltered, keeping the volume of theretentate constant (about 40 L of H₂O are added).

The recovery of iodine in the permeate is 99% compared with that presentin the solution before nanofiltration.

The collected permeate (40 L) is acidified to pH 1 with 50% H₂SO₄ (w/w).The resulting solution is oxidized at room temperature (25° C.) in acontinuous oxidation-extraction system. Oxidation is carried out feedingin line 30% H₂O₂ (w/w) to the permeate at pH 1: the aqueous solution isthen fed to a continuous laboratory extractor and the elementary iodineformed following oxidation is extracted with dodecane. The amount of 30%H₂O₂ (w/w) used is defined by monitoring the redox potential directly atthe head of the extractor keeping it at 530 mV. Volumetric ratios are 3for dodecane and 1 for the aqueous solution. 120 L of organic phase arecollected.

The extraction yield in iodine is 98% compared with the amount of iodinepresent in the permeation solution from nanofiltration.

The organic phase is again subjected to extraction in a continuoussystem with an aqueous alkali solution (30% NaOH (w/w) in volumetricratio of 1 L for 20 L of organic phase). The resulting alkaline solution(6 L) is adjusted to pH 1 with 50% H₂SO₄ (w/w). The precipitatedelementary iodine is recovered by filtration.

3225 g of iodine are obtained (92% overall yield of the process).

EXAMPLE 4

20 kg of mother liquors from Iopamidol crystallization, containing about20% (w/w) of 2-butanol (the iodine content of the mixture being 1.54%(w/w)) are adjusted to pH 12 with 30% NaOH (w/w). 4 g of CuSO₄·5 H₂O areadded and the mixture is concentrated under atmospheric pressure to 50%of the starting weight, then is refluxed to complete the mineralisation,so that the total distillation and reflux time is 6 hours.

The mineralisation yield is 100% (determined on the iodine content byargentometric titration compared with the starting content in organiciodine).

The concentrated solution is left to cool, buffered to pH 7 with 50%H₂SO₄ (w/w) and then subjected to nanofiltration, using a Separemmembrane mod.Desal5 (DK2521T) at an operative pressure of 25-30 bars.The solution is diafiltered adding water and keeping the retentatevolume substantially constant (about 20 L of H₂O are added). Thecollected permeate (20 L) is concentrated under atmospheric pressure to10 L, then acidified to pH 1 with 50% H₂SO₄ (w/w) and treated with 30%H₂O₂ (w/w) at room temperature monitoring the redox potential of thesolution, the reaction is completed when a 530 mV potential is reached.Elementary iodine is recovered by filtration through porous septum.

277 g of elementary iodine are obtained (90% overall yield of theprocess).

EXAMPLE 5

40 kg of mixture of effluents from the production of Iopamidol,containing about 15% (w/w) of organic solvents (2-butanol andtert-butanol), about 10% (w/w)2,4,6-triiodo-5-amino-1,3-benzenedicarboxylic acid and about 4% (w/w) ofIopamidol and its side-products (the iodine content of the mixture being2.5% (w/w)) are adjusted to pH 12 with 30% NaOH (w/w). 75 g of CuSO₄·5H₂O are added, the mixture is concentrated under atmospheric pressure to30% (w/w) of the starting weight, then refluxed to complete themineralisation, so that the, total distillation and reflux time is 6hours.

The mineralisation yield is 100% (determined on the iodine content byargentometric titration compared with the starting content in organiciodine).

The concentrated solution is left to cool at 15° C. for 2 hours and theprecipitated salts are filtered through porous septum. The solution isbuffered to pH 7 with 50% H₂SO₄ (w/w) and subjected to nanofiltration,using a Separem membrane mod. Desal5 (DK2521T) at an operative pressureof 25-30 bars. The solution is diafiltered, keeping the retentate volumeconstant (about 40 L of H₂O are added).

The recovery of iodine in the permeate is 99% compared with that presentin the solution before nanofiltration.

The collected permeate (40 L) is concentrated under atmospheric pressureto 20 L, then acidified to pH 1 with 50% H₂SO₄ (w/w) and treated with30% H₂O₂ (w/w) at room temperature monitoring the redox potential of thesolution; the reaction is completed when a 540 mV potential is reached.The precipitated elementary iodine is separated by sublimation in vapourstream and absorption in 30% (w/w) NaOH in the form of I⁻/IO₃ ⁻ a iodineconcentration of 3.5%. The resulting alkaline solution is adjusted to pH1 with 50% H₂SO₄ (w/w). The precipitated elementary iodine is recoveredby filtration.

910 g of iodine are obtained (91% overall yield of the process).

EXAMPLE 6

30 kg of some production wastes from the production cycle of Iopamidol,containing about 5% (w/w) of organic solvents (2-butanol, butylacetate), about 20% (w/w) of2,4,6-triiodo-5-amino-1,3-benzendicarboxylic acid and 20% (w/w) about ofIopamidol and its side-products (the iodine content of the mixture being21.5% (w/w)) are adjusted to pH 13 with 30% NaOH (w/w). 145 g of CuSO₄·5H₂O are added, the reaction mixture is concentrated under atmosphericpressure to 60% (w/w) of the starting weight, then refluxed to completethe mineralisation, so that the total distillation and reflux time is 8hours.

The mineralisation yield is 100% (determined on the iodine content byargentometric titration compared with the starting content in organiciodine).

The concentrated solution is left to cool and buffered to pH 7 with 50%H₂SO₄ (w/w). The resulting neutral solution is subjected tonanofiltration, using a Separem membrane mod. Desal5 (DK2521T) at anoperative pressure of 25-30 bars. The solution is diafiltered, keepingthe volume of the retentate constant (about 50 L of H₂O are added).

The recovery of iodine in the permeate is 99% compared with that presentin the solution before nanofiltration.

The collected permeate (50 L) is concentrated under atmospheric pressureto 20 L, then acidified to pH 1 with 50% H₂SO₄ (w/w) and treated with30% H₂O₂ (w/w) at room temperature monitoring the redox potential of thesolution; the reaction is completed when a 550 mV potential is reached.The precipitated elementary iodine is recovered by filtration.

5740 g of iodine are obtained (91% overall yield of the process).

EXAMPLE 7

40 kg of mixture of effluents from the production of Iomeprol and2,4,7-triiodo-3,5-acetamido-benzoic acid sodium salt, containing about10% (w/w) of organic solvents (n-butanol and ethanol), about 10% (w/w)of 2,4,6-triiodo-5-amino-1,3-benzenedicarboxylic acid and2,4,7-triiodo-3,5-acetamido-benzoic acid and about 4% (w/w) of Iomeproland its side-products (the iodine content of the mixture being 8.76%(w/w)) are adjusted to pH 13 with 30% NaOH (w/w). 80 g of CuSO₄·5 H₂Oare added, the mixture is concentrated under atmospheric pressure to 30%(w/w) of the starting weight; then the reaction mixture is refluxed tocomplete the mineralisation, so that the total distillation and refluxtime is 8 hours.

The mineralisation yield is 100% (determined on the iodine content byargentometric titration compared with the starting content in organiciodine).

The concentrated solution is left to cool at 15° C. for 2 hours and theprecipitated salts are filtered through porous septum. The solution isbuffered to pH 7 with 50% H₂SO₄ (w/w) and subjected to nanofiltration,using a Separem membrane mod. Desal5 (DK2521T) at an operative pressureof 25-30 bars. The solution is diafiltered, keeping the volume of theretentate constant (about 45 L of H₂O are added).

The recovery of iodine in the permeate is 99.5% compared with thatpresent in the solution before nanofiltration.

The collected permeate (45 L) is acidified to pH 1 with 50% H₂SO₄ (w/w).The resulting solution is oxidized at room temperature (25° C.) adding30% H₂O₂ (w/w) to the solution. The amount of 30% H₂O₂ (w/w) used isdefined by monitoring the redox potential considering the oxidationconcluded when a 530 mV potential is reached. The mixture is cooled to5° C. for about 3 hours and the precipitated iodine is recovered byfiltration.

3225 g of iodine are obtained (97% overall yield of the process).

What is claimed is:
 1. A process for the recovery of iodine from motherliquors or wastes containing iodinated organic compounds, bymineralisation of organic iodine and subsequent transformation of theformed iodide into elementary iodine, characterized in that the aqueoussolution is concentrated to a suitable volume during the mineralisationstep, under atmospheric pressure and at the boiling temperature, andsaid solution is purified by nanofiltration.
 2. A process as claimed inclaim 1, in which the mineralisation of organic iodine is carried out byaddition of copper ions or finely dispersed metallic copper in alkaliaqueous solution, in amounts from 100 to 3000 ppm at pH
 12. 3. A processas claimed in claim 2, in which the amount of copper ranges from 500 to1000 ppm.
 4. A process according to claim 1, in which the concentrationstep of the solution to be deiodinated is carried out under atmosphericpressure and at the boiling temperature for a time from 2 to 6 hours. 5.A process according to claim 1, in which the oxidizing agent used ishydrogen peroxide.
 6. A process according to claim 1 in which theoxidation and the recovery of iodine are carried out in a single step.7. A process as claimed in claim 6, in which the permeate fromnanofiltration is acidified to pH 0.5-1 with 50% sulfuric acid attemperatures ranging from 20° C. to 50° C., and the resulting solutionis fed to a continuous extractor feeding in line the oxidizer so as toguarantee a permanence time sufficient for the completed oxidation andextraction of iodine with a suitable solvent.